This invention relates to an electric connector and an improved contact therefor, and more particularly to an improved and novel connector having better characteristics, which has a low cost and which can be attached to a printed circuit board firmly without erroneous insertion.
Recently, connectors have been widely used in various electronic devices. For example, in order to simplify assembly of an electronic device such as a TV receiver and to simplify replacement of imperfect parts, the circuits of the device are divided into several blocks, and the blocks and the board are mutually connected by the connectors.
For the contact metal of these connectors, conventionally noble metal such as gold or rhodium is plated on the surface of the contact of the connector, and for the spring material of the connector there is used a precipitation hardened metal such as beryllium copper and titanium copper. however, although a contact made of these materials has good contact characteristics, there are disadvantages such as that it is usually expensive and that the productivity is poor due to the necessity for thermal treatment of the spring material.
As the cost is an important factor especially in consumer type electronic devices, sometimes there is used a base metal such as tin or tin-lead alloy for the contact metal, and phosphor bronze annealed at a low temperature for the spring material. However, there is also a disadvantage in a contact consisting of such a low cost material. That is, at a high temperature, phosphorus contained in phosphor bronze reacts with tin, and a very brittle chemical compound is formed between the tin and phosphor bronze. This causes exfoliation of the tin layer from the spring of phosphor bronze, and so there is caused failure of the contact.
Moreover, as the base metal has an electric conductivity lower than the noble metal and a melting point lower than gold, the current capacity of the contact of the base metal is lower than that of the contact of the noble metal. Further, when vibration is caused at the contact, insulating black powder is often produced by the contact of the base metal, and so the contact resistance is greatly increased. Therefore, when a connector using a contact of tin or tin alloy is used for an electronic acoustic device including a vibration source such as a speaker or for an electronic device employed in a mobile apparatus, there is a tendency toward contact failure. On the other hand, usually a circuit panel is inserted tightly into the connector using such a contact, which is mounted on a printed circuit board, so as to increase the contact force and thereby to compensate for poorer contact performance. However, in this case, there is another problem of deformation and sometimes cracking of the printed circuit board at the time of inserting the circuit panel into the connector or removing the circuit panel therefrom.